FR2483686A1 - METHOD FOR MANUFACTURING A SOLAR BATTERY - Google Patents

Abstract

METHOD FOR MANUFACTURING A SOLAR BATTERY, CHARACTERIZED IN THAT IT CONSISTS OF: CUTTING A TRANSPARENT ELECTRODE ON A TRANSPARENT SUBSTRATE 32 BY USING A LASER HAVING SUFFICIENT ENERGY TO FORM A PLURALITY OF TRANSPARENT ELECTRODE BANDS 34; REALIZING AN ACTIVE REGION 43 OF A SEMICONDUCTOR MATERIAL ON SAID SUBSTRATE AND SAID TRANSPARENT ELECTRODE STRIPS; CUT OUT THE SAME ACTIVE REGION USING A PARALLEL LASER AND ADJACATE THE FIRST LASER SO AS TO MAKE A TRACE THROUGH THE SAME ACTIVE REGION WITH A VIEW TO FORMING ACTIVE REGION BANDS WITHOUT FORMING TRANSPARENT ELECTRODE AND INTERCONNECTING THE ACTIVE REGION BANDS, SERIES WITH A POSTERIOR ELECTRODE.

Description

The present invention relates to solar batteries. Of

  more specifically, this invention relates to a method of

connection of series connected solar cells and cells

  tandem junction solar panels connected in series.

  We know that photovoltaic devices, that is to say

  solar cells, are able to transform the ray-

  solar energy in usable electrical energy. This transformation

  tion of energy results from the photovoltaic effect well known in the field of solar cells. The solar radiation which

  hits a solar cell and that is adsorbed by an ac-

  tive of a semiconductor material generates electrons and vacancies. These electrons and vacancies are separated by an internal electric field, for example a rectifying junction, in the solar cell. From this separation of electrons and gaps in the internal electric field result phototension and the

photocurrent of the cell.

When the area of the solar cell increases, the resistance

  series of the incident electrode to the solar radiation of the cel-

  lule also increases and this results in the obligation to

  provide larger and more complicated gate electrodes

quées to extract the current generated during the illumination

  of the solar cell by sunlight. The fact of

quer solar cells in long narrow strips and

stringing the strips in series eliminates the need for pre-

  see complicated grid configurations. However, until now, the manufacture of thin strips of solar cells connected in series, or tandem junction solar cells connected in series required the application of techniques of

  chemical etching and photolithographic techniques. The utility

  The use of these techniques often results in the formation of pinheads (shrinkage) in semiconductor materials, which shortens and damages all or part of the solar cell. In addition, the photolithography technique is not easily adaptable to continuous processing on a large scale and it results in a strong

  increase in the manufacturing price of connected solar cells

  tees in series. Therefore, it is highly desirable to

have a process for manufacturing connected solar cells

tees in series or connected tandem junction solar cells

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  serial tees that do not have many milking stages

liquid. This is precisely the aim of the present invention.

tion. The invention relates to a method of manufacturing a solar battery connected in series and a tandem junction solar battery, connected in series, using the technique of laser tracing or cutting. This process uses, among other things, the laser cutting of a transparent conductive oxide deposited on a transparent strip substrate. Then the semiconductor material is deposited on the transparent substrate and on the transparent conductive oxide strips. Conductive oxide

  transparent constitutes the upper contact of the device. This dis-

positive then undergoes laser cutting in order to divide into

  strips the semiconductor material without affecting the trans-

  parent driver. The strips are parallel and adjacent to the cutting strips previously formed by laser. Then a posterior metallic contact is applied to the oxide strips

transparent conductor and semiconductor material and we e-

finally performs a laser tracing or cutting parallel and adjacent to the two laser cuts previously made (but spaced from them) in order to obtain a device which is connected in series. Individual panels of solar cells connected in series and solar cells with tandem junction can be connected in parallel so as to obtain any desired voltage and current. The semiconductor materials, the transparent conductive oxides and the posterior electrodes used during the manufacture of the solar battery must be chosen.

so that a single laser is needed to perform the

  cutting each successive layer with decreasing energy

or that lasers of different wavelengths are needed

to cut a layer without affecting the other layers. Alternatively, for example,

  very short laser pulses of the order of 10 to 20 nanose-

conditions and significant pulse frequencies of the order of

0.2 to 5 MHz to cut a layer without affect

ter the other layers.

Other features and advantages of this invention

  will emerge from the description given below with reference to

  attached drawings which illustrate various examples of embodiment

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  devoid of any limiting character. In the drawings:

  - Figure 1 illustrates, in cross section, a battery so-

tandem junction hydrogenated amorphous silicon glass, manufactured

  according to the present invention from a plurality of cells

tandem junction sunglasses; - Figures 2a to 2f illustrate the method of manufacturing a series of interconnected solar cells, according to an embodiment of the method according to this invention, and - Figures 3a and 3b illustrate a variant of the invention, provided for interconnect solar cells after

steps illustrated in Figures 2a to 2e.

  Firstly, reference is made to FIG. 1 which illustrates a cross section of a tandem junction solar battery made from a plurality of interconnected tandem junction solar cells. The tandem junction solar battery 10 comprises a series of tandem junction solar cells 20, 21 and 22, connected in series on a substrate 32. For example, the solar cells are manufactured using the materials described in American patent n 4,064,521, and in patent applications

American No. 70,513, filed August 28, 1979 and No. 109,637,

  asked on January 4, 1980. As a variant, the amorphous silicon can be produced with modifiers in addition to hydrogen and it is possible to use silanes such as halogens, silicon vaporized or having undergone a cathode sputtering or other semiconductor materials , such as OdS, CdSe, CdTe, Cu2S and the like.

  Each tandem junction 20, 21 and 22 solar cell includes

  takes a transparent conductive oxide strip 34, as

  incident electrode and two or more active layers 38 and 42 de-

  semiconductor material9 separated by a tunnel junction 40.

The active layers have regions 38a, 58b and 38c and 42a, 42b and 42c of different conductivity types. The layer (s)

semiconductors and tunnel junctions will be designated below

collectively after by the term "active region" 43. This re-

  gion active 43 has a straightening junction either inside

of the region, i.e. a PN junction, either at its

  face, that is to say a Schottky barrier. The active region 43

  may be a layer of semiconductor material or a plurality of

  lity of semiconductor layers as described above. Tandem junction solar cells are interconnected with

a rear electrode 44 and ureconnection series 46.

Laser cutting or tracing is used to make strips from the transparent conductor 34 and the semiconductor layers 38 and 40. The bands of conductive oxide trans-

  parent are parallel and adjacent to the strips of semi material

  driver. The laser cutting technique also makes it possible to produce solar structures which have strips

of a single active region of semiconductor material 38, connected

  tees in series. The transparent incident electrode, the semiconductor material and the material constituting the posterior or back electrode, must be chosen so that a laser of single wavelength but of variable power, decreasing from the power necessary for cutting of the incident electrode,

could cut out the devices. Alternatively, the materials may

can be chosen so that a laser emitting light at a frequency can trace or cut a material, for example, siliconramorph, but not another material such as oxide

transparent conductive.

After this description of the structure of a solar cell

  completed 10, refer to Figures 2a to 2f which illustrate the manufacturing technique. The process used in this

example refers to the production of a solar sili battery.

hydrogenated amorphous cium.

  FIG. 2a represents a substrate 32 constituted for example

  glass, plastic and the like. Figure 2b shows

  feels the substrate 32 covered with a transparent conductive oxide 54, as an incident electrode, made of a material such

  than tin and indium oxide, tin oxide and the like.

  The transparent conductive oxide is deposited by vaporization or by cathode sputtering or any other process well known to technicians. As a variant, the glass substrate 32, covered with a

  transparent electrode material such as tin oxide and has in-

dium is commercially available. The transparent and conductive electrode material 34 should have a thickness of the order of 6.5 nanometers and a layer resistivity of less than about 150 ohms per square, preferably less than about

100.a per square.

Referring to FIG. 2c, it can be seen that the substrate 32 which comprises the layer 34 of transparent conductive oxide is cut into strips n using a laser. The laser can be of any type capable of cutting the transparent conductive oxide. One can use for example a laser YAG with neodyne continuously excited, radiating at 1.06 / um and controlled according to a switching mode Q. with an average power of the order of 4.5 watts, a pulse frequency of the order of 56 K Hz and a cutting speed

about 20 cm / second.

Then, as illustrated in FIG. 2d, the active region 43 is deposited on the incident electrode strips. The substrate 32 comprising the layer 34 of transparent conductive oxide and the active semiconductor region 43 is further cut by laser, parallel to and adjacent to the previous cut up to the transparent electrode, as shown in FIG. 2a. For example, a continuously excited neodymium YAG laser, radiating at 1.06 / µm and operating at a pulse frequency

of 36 KHz, a cutting speed of 20 cm / second and a power-

  sance set to 1.7 watts is enough to cut silicon

  hydrogenated amorphous and a cermet up to transparent oxide bands

  rent driver 34 but without passing through them.

  As shown in Figure 2f, an electrode material

  posterior, made of titanium, aluminum, indium or similar

  the area is evaporated angularly on the bands of the cell so-

  laire for example at an angle of about 30 to 450 relative to a perpendicular to the substrate 32, so that the material forms strips 46 which interconnect in series the

individual cells. Finally, contacts 50 and 52 are connected

  ties to the solar battery structure by any known process.

As a variant, the material of the posterior electrode can be vaporized, cathodically pulverized or deposited by any known method, over the entire posterior part of the strips of semiconductor material, as shown in FIG. 3a and then this material is cut by laser , parallel to the laser cutting having formed the groove illustrated in FIG. 2e. The groove is adjacent to the groove shown in Figure 3b. A continuous excitation neodymium YAG laser cutting, carried out using a similar pulse frequency and an identical speed, but with a power of the order of 1.5 w, is sufficient to trace the contact. posterior electric forming a groove

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  born without cutting the semiconductor or oxide layers

  transparent conductor. This zabricetion technique is applied

cable to semiconductor materials in which resistivity

lateral surface is sufficiently high for example upper

  less than 1010- <L per square, so that the electrical contact, applied to the two walls of the semiconductor strips

  do not exit the cells. We can use for this purpose

  fet of hydrogenated amorphous silicon, cermets and the like. If the semiconductor or other materials used to form the active region, have low surface resistivity

lateral, the edge of the region should be protected

tive using an appropriate dielectric material, before con-

nect the strips in series.

  This invention will now be described by the following nonlimiting examples. Of course, any variant

  is within the reach of ordinary skill in the art.

: EX EP LE 1

  A glass substrate having dimensions of 7.6 x 7.6 cm,

  covered with a layer of indium tin oxide having a thick-

  seur of the order of 250 nanometers and a resistivity of about ohms per square, manufactured by the British company "Triplex Glass Company, Ltd", Kings Norten, Birmingham, was cut by - laser, using a YAG laser with neodymium with continuous excitation and switching to Q code, with a power of 4.5 watts, a pulse frequency of 36 Khz, a tracing speed of 20 cm / sec and a focal distance of the order of 27 mm. The laser cutting formed a groove having a width of about 0.002 cm

  between strips of tin and indium oxide 0.5 cm wide.

  The underlying glass has melted slightly in places on a nro-

  founder of a few hundred Angstroms. After the laser cutting, the conductivity on the cut area was measured and it

was found to be slightly conductive. The slightly conductive area

was removed by immersing the substrate in a solution of a concentrated hydrochloric acid wax in two parts of water,

  for a duration of approximately 45 seconds.

Next, the active semiconductor region comprising the

  cermet PtSiO2, having a thickness of about 15 nanometers, con-

holding approximately 123X by volume of platinum, a doped skin of type P + of hydrogenated amorphous silicon with a thickness of the order

of 36 nanometers9 an undoped layer of hydro-amorphous silicon

  gene having a thickness of about 590 nanometers, and a layer

  final of hydrogenated amorphous silicon doped in N + type, of a thick-

36 nanometer, was deposited on the substrate and the bands of indium and tin oxide by the methods described in the American patent n ° 4 167 051. The amorphous silicon was deposited by luminescent discharge in a atmosphere containing -silicon,

hydrogen and appropriate conductivity modifiers

prayed. The cermet was formed by co-sputtering of

platinum (Pt) and silica (SiO2).

The active semiconductor region has been cut out by tracing

using the laser mentioned above, in order to form rai-

  nures in the active semiconductor region, parallel but offset from the initial laser cutting. The laser operated at a power of 1.7 watts and with a distance

  48 mm focal length, pulse frequency and uncovering speed

  page being identical to those indicated previously. The width

of the groove thus drawn was about 0.005 cm. The depth

the cut-out was sufficient for the groove to go

  up to the transparent conductive oxide, without however crossing it

  Then, the bands and the active region as well as the transparent substrate were coated with a posterior titanium electrode to a thickness of the order of 100 nanometers. The cell was cut for a third time to form a groove in the posterior electrical contact, this groove being parallel and adjacent to the previous cuts, using a laser.

operating at a power of approximately 1.3 watts, with a dis-

focal length of the order of 75 mm and the pulse frequencies as well as the cutting speeds indicated above. Copper bands were attached to the ends of the electrodes using an epoxy silver cement. Finally we removed the electric shunts by applying a reverse polarization of 5 volts to

each cell.

The cell manufactured according to the process indicated above was tested with a light whose intensity was equivalent to, a sunlight of 1 AM. A solar battery made up of 12 individual strips of solar cell had a

  Voc voltage of 9.3 volts, approximately 0.775 volts per cell, one cou-

  short-circuit rant J of the order of 5.3 milliamps per cm2, a load factor of approximately 0.51 and a yield of the order

2.1%.

EXAMPLE II

  A solar battery connected in series was manufactured according to the technique indicated in Example I, however the metal of the posterior contact was indium and it was vaporized on the active region of the semiconductor device at the same time as

  tin and indium oxide. Then grooves were cut.

swords in indium by laser tracing using a laser power of 1.3 watt, parallel and adjacent to

laser-traced grooves in hydrogenated amorphous silicon.

After fixing the electrodes and eliminating electrical short circuits, the solar cell made up of 10 strip cells

  connected in series, had a voltage in

cooked open at 7.9 volts, a short-circuit current of 4.6 mil-

  lamps per cm, a load factor of 0.51 and a yield of 1.9% o when exposed to a test light with

an intensity of the order of 1 AM.

EXAMPLE III

  A 7.6 x 7.6 cm glass substrate covered with a layer of indium tin oxide having a resistivity of the order of 104 (2-per square was cut by tracing with Using a laser, according to the process defined in Example I. Next, a tandem junction structure comprising a platinum cermet, a layer of amorphous silicon, a tunnel junction and a second layer of amorphous silicon, was deposited on the substrate and bands of tin and indium oxide. The thickness of the cermet layer was of the order of 7.5 nanometers. The first layer of amorphous silicon, having a Pl type region a thickness d "about 30 manometers, an intrinsic region whose thickness was around 76 nanometers and an N-type region, was deposited on the platinum cermet. A tunnel junction of a platinum cermet of 7.5 manometers thick was deposited on the amorphous silicon layer. The second layer of

  amorphous silicon, having a P-type region an intrinsic region

  and an N-type region with thicknesses of 30 nanometers, 408 nanometers and 45 nanometers., respectively, has been deposited on the tunnel junction. The regions of amorphous silicon have been

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  deposited by luminescent discharge and the platinum cermets have

  been deposited by cathodic co-sputtering of platinum and

  running. These layers were cut by laser tracing in order to form a groove parallel and adjacent to the tracing carried out previously, using a laser operating under the conditions indicated in Example I with a power of 1.7 watts. The

grooves thus produced were adjacent and parallel to the ra-

  nures described with reference to Figure 2a. Then, a layer of tin having a thickness of 100 nanometers was vaporized at an angle of the order of 30, relative to the perpendicular to the substrate, as shown in FIG. 2f. Bands of

copper were attached to the electrode using an epoxy cement

silver. Electrical short circuits have been eliminated by

application of a reverse bias voltage.

The solar battery was made up of available cells--

  seated horizontally in series with two cells vertically in tandem for a total of 20 cells. The device had an open circuit voltage of 11.8 volts when exposed to

a light with an intensity of 1 AM. - -

  Obviously, this invention is not limited to the various embodiments described and / or shown.

  here but that it encompasses all variants.

Claims (15)

  1.- Method of manufacturing a solar battery, characteristic   rised in that it consists in: cutting a transparent electrode on a transparent substrate (32) using a laser having sufficient energy to form a plurality of transparent electrode strips (34); producing an active region (43) of a semiconductor material on said substrate and said transparent electrode strips; cutting said active region using a laser parallel to and adjacent to the first laser so as to trace through said active region in order to form bands of active region without forming a transparent electrode and interconnect said bands of active region, series with - a posterior electrode.   2.- Method according to claim 1, characterized in that said transparent electrode, said active region (45) and said posterior electrode are chosen so that the laser requires a greater power to cut the transparent electrode than to cut said region active and a higher power for cutting said active region than for cutting said posterior electrode.   3.- Method according to claim 2, characterized in that said active region consists of a semiconductor material chosen from the group which includes: amorphous silicon hydro-   gene, vaporized silicon, silicon having undergone a pulveri cathodic station, CdS, CdSe, CdTe and Cu2S.   4.- Method according to claim 3, characterized in that said active region consists of a plurality of layers of semiconductor material.   5.- Method according to claim 3, characterized in that   0 said active region consists of amorphous silicon.   6.- Method according to claim 5, characterized in that said laser is a neodymium YAG laser excited continuously, emitting light having a wavelength of the order 1.06 / µm.   7.- Method according to claim 6, characterized in that   said laser is controlled in switching mode Q with a frequency   repetition rate of the order of 36 KHz. 8.- Method according to claim 7, characterized in that crumb   said tracing or cutting is carried out by said functional laser-   1O nant with an energy of the order of Il5 Watts in order to trace said transparent electrode material and with an energy of the order   of 1.7 Watt, to trace said active region.   9.- Method according to claim 8, characterized in that said active region comprises a plurality of layers of sili- hydrogenated amorphous cium.   10.- Method according to claim 9, characterized in that each pair of adjacent layers of hydrogenated amorphous silicon   (38, 42) is separated by a tunnel junction (40).   110- Method according to claim 10, characterized in that   that said tunnel junction consists of a cermet.   12.- Method according to claim 11, characterized in that said rear electrode is produced by angular evaporation. 13. Method according to claim 1, characterized in that said rear electrode is produced on the strips of the active region and of the transparent electrode, laser of said posterior electrode then being produced in parallel simultaneously and adjacent to the cutting of the strips of the active region.   14.- Method according to claim 1f, characterized in that the laser cutting of the posterior electrode is carried out   with an energy lower than that which is necessary for. perform the cutting of the active region and in that the seam ripper of said active region requires less energy than that required for cutting the transparent electrode.   15.- Method according to claim 14, characterized in that   that the active region consists of amorphous silicon hydro- 16.- A method according to claim 15, characterized in that said laser is a continuously excited neodymium YAG laser, emitting light which has a wavelength of approximately 1.06 µm. 17.- Method according to claim 16, characterized in that said laser is controlled according to a switching mode Q. 18.- Method according to claim 17, characterized in that said active region consists of a plurality of layers hydrogenated amorphous silicon. 1 1 12 2483686 19.- Method according to claim 18, characterized in that that each pair of adjacent layers of amorphous silicon hydro-   gene is separated by a tunnel junction.